Currently, usually a flat panel display is used in the field of displays, and the majority of flat panel displays are an AMLCD (Active Matrix Liquid Crystal Display). Existing AMLCD comprises a TFT (thin film transistor) array substrate, as large-area production of a-Si at a low temperature can be easily achieved and the production technology is relatively mature, it is currently a widely used material for manufacturing the TFT array substrate. However, the band gap of the a-Si material is only 1.7 eV, it is opaque to visible light and is photosensitive within the range of the visible light, thus an opaque metal mask plate (black matrix) needs to be added to shield the light, correspondingly the complexity of the production process of the TFT array substrate is increased, then the cost is increased and the reliability and opening rate are lowered. Meanwhile, to obtain enough brightness, the light strength of a light source needs to be enhanced, and correspondingly power consumption is increased. In addition, the mobility of the a-Si material can hardly exceed 1 cm2·V−1·s−1, thus current TFT array substrates can hardly meet needs of liquid crystal televisions with a continuously increasing size and drive circuits with better performance.
As the a-Si TFT array substrate has the above disadvantages, an oxide semiconductor TFT has been widely paid attention due to its various advantages and has been undergoing fast development during recent years. An oxide semiconductor, being transparent and having a high mobility, fine uniformity and a simple fabrication process, can better meet needs of large-sized liquid crystal displays. Also, the production of the oxide TFT can satisfactorily match current LCD production lines, then the transition is easy, thus people have paid more attention to the oxide TFT which has been a hot research topic recently.
However, the prior art need to use at least 4 masking exposing processes during manufacturing the oxide TFT array substrate, then the production process is very complex and the cost of the mask plate is high, correspondingly the production cost of the product is increased, the yield of the product is lowered, and equipment capacity is decreased.